Assessments of population size were derived via direct counting of individuals, except for the relatively large population of D. falcata on Oahu, where four local populations were described with the help of ten1m×1msample plots, in which all individuals and their life stages were recorded. To describe the stage structure of the population, the following stages were distinguished: gametophyte; sporeling (young sporophyte); premature (pre-reproductive sporophyte); mature (reproductive sporophyte); dormant and (or) dead. Although the gametophyte stage is an important one for the recruitment of fern populations, gametophytes are extremely difficult to observe in field conditions. This stage is the most vulnerable, depending on microedaphic and microclimatic conditions (Peck et al. 1990). Where possible, however, the numbers of gametophytes were still counted, but there may be gaps in the data. Also, since Diellia ferns are inhabitants of dry and mesic forest communities, they evidently possess a certain ability to survive dry periods in a dormant stage (Wagner 1952). The duration of possible dormancy has not yet been studied. Therefore, in the case of dry looking plants, we were not able to decide whether they were dead or dormant, and pooled these stages together. For these reasons, only the stages of sporophyte generation
(sporeling, premature, mature) were used in later population analyses.